$ \left(\dfrac{8}{5}\right)^{3}$
Explanation: $= \left(\dfrac{8}{5}\right)\cdot\left(\dfrac{8}{5}\right)\cdot \left(\dfrac{8}{5}\right)$ $= \dfrac{64}{25}\cdot\left(\dfrac{8}{5}\right)$ $= \dfrac{512}{125}$